1. Field of the Invention
The present invention relates to an optical adaptor for endoscope which is detachable to a distal part of an endoscope insertion portion and an endoscope apparatus.
2. Description of the Related Art
It is well-known that an endoscope has widely been used in the medical and industrial fields. The endoscope for medical field observes the organ in the body cavity by inserting an elongated insertion unit into the body cavity, and performs various treatments by using a treatment tool inserted in a treatment tool channel if necessary.
Further, in the industrial field, the endoscope observes and treats the scratch or corrosion of a jet engine or a tube of a power plant by inserting an elongated insertion unit thereto.
A bending portion is arranged at the distal end of the endoscope insertion portion and an endoscope operation portion is operated to bend the bending portion, thereby changing the observing direction of an objective at a distal part of an observation optical system arranged in the endoscope insertion portion.
An illumination optical system for illuminating an inspection part observed by the objective at the distal part of the observation optical system is arranged at the bending portion and the distal part of the endoscope insertion portion. It is well-known that a plurality of light-emission diodes (hereinafter, referred to as LEDs) are used for illumination of the illumination optical system and is put into practical use.
Incidentally, the LED has excessively weak property to the static electricity. Therefore, there has been a problem that in applying an electrostatic voltage between the anode and the cathode of the LED, serving as the positive and negative electrodes of the LED, the LED is broken due to the static electricity.
In consideration of the above-mentioned problem, Japanese Unexamined Patent Application Publication No. 2002-95624 discloses a technology for preventing the electrostatic break of the LED due to applying an electrostatic voltage between both the anode and the cathode of the LED by connecting an electrostatic protecting circuit comprising an inductor, capacitor, and a diode between the anode and the cathode of the LED.
Further, Japanese Unexamined Patent Application Publication No. 2000-92479 discloses a technology for preventing the electrostatic break of a power supply circuit due to applying an electrostatic voltage with a simple circuit structure by connecting, a transistor and a diode, to a power supply circuit including an illuminating circuit arranged at a distal part of an endoscope insertion portion.